
Benton County Lake Quality
Iowa, 2 lakes, average grade F (Algae-prone)
Benton County has 2 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. Every one of those lakes carries an A–F grade, so the county-level summary covers the full set rather than a monitored subset. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Hannen Lake (F); the most-stressed is Hannen Lake (F).
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Quick Answers for Benton County
Planning a trip? Check special fishing regulations for Hannen Lake — or check the official Iowa fishing regulations.
All Lakes in Benton County
2 lakes2 graded lakes
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | FHannen LakeBenton | F | 1.2 ft | 141 µg/L | 119.9 µg/L | No recent samples | Not recorded |
| 2 | FRodgers LakeBenton | F | 2.6 ft | 91.5 µg/L | 44.5 µg/L | No recent samples | ✓ Public |
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Other Counties in Iowa
See how Benton County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.